Add pubsub example.

examples/pubsub/main.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"log"
+	"time"
+
+	"github.com/libp2p/go-libp2p"
+	libp2pquic "github.com/libp2p/go-libp2p-quic-transport"
+	bootutil "github.com/wetware/casm/pkg/boot/util"
+	"github.com/wetware/ww/pkg/client"
+	"github.com/wetware/ww/pkg/vat"
+)
+
+func main() {
+	ctx := context.Background()
+
+	// Instantiate the libp2p host that the Wetware client will use.
+	host, err := libp2p.New(
+		// Don't listen for incoming network connections.  This is
+		// common practice for Wetware clients.
+		libp2p.NoListenAddrs,
+		// Wetware uses the QUIC transport, so let's enable it.
+		libp2p.Transport(libp2pquic.NewTransport),
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer host.Close()
+
+	// Create a bootstrap service, capable of locating active peers
+	// in the cluster. To keep things simple, we will use multicast
+	// UDP over the loopback interface. In rare cases, you MAY need
+	// to change 'lo0' to some other value.
+	const addr = "/ip4/228.8.8.8/udp/8822/quic/multicast/lo0"
+
+	// Dial into the network interface to obtain a bootstrapper.
+	boot, err := bootutil.DialString(host, addr)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer boot.(io.Closer).Close()
+
+	// Instantiate the dialer.  This will locate a cluster node,
+	// connect to it, and return a *client.Node.
+	dialer := client.Dialer{
+		// This represents the client's Cap'n Proto vat, which is
+		// analogous to a 'Host' in libp2p parlance.
+		Vat: vat.Network{
+			NS:   "ww", // the default cluster namespace
+			Host: host,
+		},
+
+		// Create a new multicast surveyor and assign it to the
+		// bootstrap discovery service.
+		Boot: boot,
+	}
+
+	// Dial into the cluster.  This returns a *client.Node, which
+	// is the main client interface to the Wetware cluster.
+	cluster, err := dialer.Dial(ctx)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer cluster.Close()
+
+	log.Printf("joined cluster")
+
+	// Join a PubSub topic.
+	topic := cluster.Join(ctx, "pubsub-example")
+
+	// Publish a message periodically in a separate goroutine.
+	go func() {
+		msg := fmt.Sprintf("hello from %s", host.ID())
+		for {
+			err := topic.Publish(ctx, []byte(msg))
+			if err != nil {
+				log.Fatal(err)
+			}
+
+			time.Sleep(time.Second)
+		}
+	}()
+
+	// Subscribe to the topic, so that we can receive updates.
+	sub, err := topic.Subscribe(ctx)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer sub.Cancel()
+
+	for {
+		b, err := sub.Next(ctx)
+		if err != nil {
+			break
+		}
+
+		log.Println(string(b))
+	}
+}